1. Field of the Invention
The present invention pertains to safety penetrating instruments and, more particularly, to safety penetrating instruments for use in forming portals for endoscopic procedures having safety members spring biased to an extended protruded position to protect against inadvertent contact with tissue of sharp penetrating members.
2. Discussion of the Prior Art
Safety penetrating instruments are widely used in medical procedures to gain access to anatomical cavities for performing endoscopic procedures, particularly laparoscopic procedures in the anatomical cavity. A well accepted type of safety penetrating instrument, as exemplified by U.S. Pat. No. 4,535,773 to Yoon, the Endopath trocar marketed by Ethicon EndoSurgery and the Surgiport trocar marketed by United States Surgical Corporation, includes a portal sleeve or cannula, a penetrating member received in the portal sleeve and a safety shield spring biased to move to an extended, protruding position to cover the sharp tip of the penetrating member once the penetrating member has entered the anatomical cavity. Accordingly, the safety shield protects tissue and organ structures within the anatomical cavity from accidental injury by contact with the sharp tip of the penetrating member after penetration or puncture of the anatomical cavity wall.
When the penetrating procedure is commenced, the distal end of the safety penetrating instrument is placed in contact with the anatomical cavity wall; and, as force is exerted on the safety penetrating instrument, contact of the safety shield with the cavity wall moves the safety shield proximally to a retracted position against the spring bias to expose the sharp tip of the penetrating member to permit the sharp tip to penetrate the cavity wall. Accordingly, the force required to penetrate the cavity wall includes not only the force required to pass the safety penetrating instrument through the anatomical cavity wall but also the force required to overcome the spring bias on the safety shield. Once the sharp tip of the penetrating member has entered the cavity, the spring bias on the safety shield overcomes the reduced proximal force on the safety shield causing the safety shield to move distally to the extended, protruding position, In practice, however, a residual proximal force is still applied to the safety shield after penetration of the sharp tip into the cavity due to contact with surrounding tissue and/or tissue trapped between the safety shield and the portal sleeve and/or the penetrating member, and the residual force is capable of preventing distal movement of the safety shield to the extended position. To assure distal movement of the safety shield upon entry of the safety penetrating instrument into the anatomical cavity, the strength of the spring biasing the safety shield distally can be increased; however, increasing the strength of the bias spring also increases the force required to penetrate the cavity wall which is undesirable. Accordingly, currently available safety penetrating instruments with safety shields utilize bias springs of strengths compromising force-to-penetrate and assured safety shield distal movement in an attempt to satisfy both requirements.
In order to provide surgeons with a sense of security, currently available safety penetrating instruments with safety shields utilize a mechanism for locking the safety shield in the distally protruded position after entry into the anatomical cavity; however, the need for a locking mechanism from a purely medical standpoint is not well established in that it is possible that a locked safety shield could cause damage upon inadvertent contact with tissue whereas an unlocked safety shield would move proximally against the spring bias like a shock absorber. It would be desirable to provide a safety penetrating instrument that provides both a sense of security to the surgeon and a shock absorbing effect.
Another type of safety penetrating instrument is exemplified by the Woodford Spike marketed by Dexide, Inc. wherein a cannulated penetrating member is disposed within a portal sleeve and a safety probe is disposed within the penetrating member and spring biased distally to extend beyond the sharp distal tip of the penetrating member upon entry into an anatomical cavity to provide a measure of protection against incidental contact with tissue within the anatomical cavity by the sharp tip of the penetrating member. Accordingly, the bias spring strength for the safety portal must be selected to compromise both force-to-penetrate and assured distal movement in the same manner as discussed above with respect to safety penetrating instruments with safety shields.